Causes and Risk Factors of Diarrhea

Diarrhea is a common problem that can come on suddenly or be a chronic complaint. Some possible causes of diarrhea include food poisoning, infections, food allergies or intolerances, and medication. There are also some conditions that cause chronic diarrhea that run in families or, rarely, have a genetic basis.

You can reduce your risk of acute diarrhea by learning good food safety and cleanliness habits, whether at home or while traveling.

Common Causes of Acute Diarrhea

The most common cause of diarrhea, especially that which starts suddenly (acute diarrhea), is an infection. This can be bacterial, viral, or parasitic and include:

• Food poisoning
• Traveler's diarrhea
• Stomach flu

Food Poisoning

Food poisoning occurs when you eat food that is contaminated with bacteria. The bacteria build up toxins in the food that make you sick.

Causes of food poisoning are poor sanitation, improper food handling, and food being stored at the wrong temperature.

• How long diarrhea lasts: Usually less than two days
• Triggered by: Toxins in food
• When symptoms appear: Within two to six hours of ingesting the food
• Appearance: Explosive, watery
• Other symptoms: Abdominal cramps, fever, vomiting, weakness

Traveler’s Diarrhea

Traveler’s diarrhea is caused by eating food or drinking water that is contaminated with bacteria or parasites. If you have diarrhea and recently traveled or drank untreated water from a stream, river, or pond (in the U.S. or elsewhere), call your doctor.

• How long diarrhea lasts: Usually less than one week
• Triggered by: Food or water that is contaminated by bacteria, viruses, or parasites
• When symptoms appear: Within 12 to 24 hours
• Appearance: Explosive, watery, sometimes contains mucus or blood
• Other symptoms: Possible vomiting and/or fever

Stomach Flu

Stomach flu, also known as gastroenteritis, is caused by a virus, but not the same that causes seasonal flu (influenza). Examples of viruses that can cause stomach flu are rotavirus and norovirus. Gastroenteritis also can be caused by a bacterium or a parasite.

• How long diarrhea lasts: Usually three to eight days
• Triggered by: A virus, bacterium, or parasite
• When symptoms appear: Within two days of exposure
• Appearance: Watery
• Other symptoms: Vomiting, fever, achiness

Common Causes of Chronic Diarrhea

Diarrhea that goes on for weeks or months may be caused by an infection, or it may be caused by an underlying medical condition or one of many other potential causes, some of which include the following:

Celiac Disease

If you have untreated celiac disease, you may have a hard time linking your symptoms with a specific food because your gut is damaged and you may experience symptoms all the time.

• How long diarrhea lasts: More than four weeks
• Triggered by: Gluten
• Appearance: Large, bad-smelling stools that float and may appear greasy
• Other symptoms: Unintended weight loss, lack of energy, lack of growth in children, as well as many other possible symptoms

Food Allergy

Symptoms of classic Ig-E mediated food allergy begin within minutes to hours of eating a trigger food. It is possible to be allergic to any food, but a few foods cause the most common food allergies.

• How long diarrhea lasts: Usually less than 24 hours
• Triggered by: A specific food
• When symptoms appear: Within two hours
• Appearance: Watery, may contain blood
• Other symptoms: Hives; vomiting; swelling of face, tongue or throat; eczema

Food Intolerance

Food intolerance is caused by a lack of the enzymes needed to digest a specific food. Lactose intolerance, the inability to digest the sugars in milk, is the most common, but it's possible to be intolerant of other foods as well.

• How long diarrhea lasts: More than four weeks
• Triggered by: A specific food
• When symptoms appear: Two to 12 hours
• Appearance: Watery, sometimes contains mucous
• Other symptoms: Gassiness, abdominal cramps or pain

Infants usually show signs of protein intolerance within a few months of birth. Some infants may react to food proteins present in breastmilk while others may react to formulas based on either cow’s milk or soy.

• How long diarrhea lasts: More than two weeks
• Triggered by: Dairy or soy products, sometimes by egg or other proteins
• When symptoms appear: Two hours or more
• Appearance: Streaks of mucous or blood
• Other symptoms: Distended belly, crying, failure to thrive

Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) includes Crohn's disease and ulcerative colitis, both of which have chronic diarrhea as a symptom. Both are incurable chronic diseases of the digestive tract that may be treated with surgery or managed with medication.

• How long diarrhea lasts: More than four weeks
• Triggered by: Not related to a specific food
• Appearance: Blood or mucous in stool
• Other symptoms: Abdominal pain, fever, weight loss, delayed growth in children

Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) describes chronic diarrhea, constipation, and abdominal pain that does not have a known disease as a cause.

• How long diarrhea lasts: At least six months
• Triggered by: Not related to a specific food, though certain foods may aggravate symptoms
• Appearance: Small, frequent stools
• Other symptoms: Chronic abdominal bloating or distention; constipation; pain relieved by bowel movement

Medication

Some medications, in particular antibiotics and chemotherapy, can cause diarrhea, as well as laxatives containing magnesium. You may have a reaction to the medication itself or an additive, such as a flavoring.

A medication may also alter the balance of bacteria in your gut, causing abdominal pain and diarrhea. Sometimes the cause of diarrhea is taking too many laxatives or longer-term abuse of laxatives.

Talk to your doctor if you have diarrhea after starting a new medication.

Genetics

There are congenital diarrheal disorders linked to specific genes. These disorders usually come on in the first few months of a child's life. They are often most common in certain populations, although congenital chloride diarrhea is one that appears worldwide.

Some other conditions that may cause chronic diarrhea also tend to run in families, including celiac disease, some forms of lactose intolerance, and food allergies.

Lifestyle Risk Factors

A change to your diet, such as going on a mostly liquid diet, eating too much fiber, or eating spicy foods may lead to diarrhea.

Beyond examining and, perhaps, adjusting what you eat and rink, other habits and exposures can put you at greater risk for diarrhea:

Personal Hygiene

The bacteria, viruses, and parasites that cause traveler's diarrhea and stomach flu are spread by contact with contaminated surfaces, food, and water. In the medical world, this is called the fecal-oral route. To reduce your risks, wash your hands well after using the bathroom, changing your child's diapers, and before eating. If you don't have access to soap and water, use an alcohol-based hand gel.

Never drink untreated water from a natural source, such as a stream. Even in developed countries, they can be contaminated with diarrhea-causing parasites spread by wildlife, such as Giardia.

When traveling to areas that have a higher risk of contaminated water and food, drink only bottled water and don't use ice unless it is from bottled or purified water. Avoid uncooked vegetables and fruits (unless they can be peeled), raw shellfish, undercooked meat, and dairy products.

Improper Food Handling

Since food poisoning is often caused by improper food handling, it's wise to follow these tips outlined by the Centers for Disease Control and Prevention:

• Clean: Keep your kitchen clean; wash utensils and cutting boards with hot, soapy water.
• Separate: Raw meat, seafood, poultry, and eggs should be kept separate from other food. Use a separate cutting board for these items.
• Cook: Use a food thermometer to ensure meat is cooked to an internal temperature that will kill the bacteria that cause food poisoning.
• Chill: Be sure your refrigerator is kept below 40 degrees. Thaw frozen foods in the refrigerator or microwave, not out on the counter.

When to See a Doctor

Diarrhea in adults typically goes away on its own, but if it lingers it can lead to dehydration (and related consequences like organ failure, seizures, or even death) or be a symptom of an underlying medical condition.

Seek medical care if you have any of the following:

• Diarrhea lasting more than two days
• Fever of 102 degrees F or higher
• Frequent vomiting
• Six or more loose stools in 24 hours
• Severe pain in the abdomen or rectum
• Stools that are black and tarry or contain blood or pus
• Symptoms of dehydration

Infants

Diarrhea can be particularly dangerous for infants and young children because dehydration can happen quickly. It's important to make sure your infant is feeding frequently if they have diarrhea and that you seek medical care immediately if your baby or young child has any of the following:

• Diarrhea lasting more than 24 hours
• Fever of 102 degrees For higher
• Severe pain in the abdomen or rectum
• Stools containing blood or pus
• Stools that are black and tarry
• Symptoms of dehydration which, in young children, can differ from those in adults

Frequently Asked Questions

Why did I get diarrhea out of nowhere? 

Diarrhea that comes on suddenly is typically caused by a bacterial, viral, or parasitic infection. Common sources of infection are food poisoning, traveler’s diarrhea, and viral gastritis, also known as the stomach flu.

What does chronic diarrhea indicate?

Diarrhea that goes on for weeks or months can be caused by an infection, underlying medical condition, or certain foods. Celiac disease, food allergies or intolerances, medications, irritable bowel syndrome, or inflammatory bowel disease can all cause chronic diarrhea and should be evaluated by your doctor.

How long should you wait to see a doctor for diarrhea? 

Diarrhea that lasts more than two days for an adult or more than 24 hours in children should be seen by a doctor. Other symptoms that warrant medical care when accompanying diarrhea include signs of dehydration, a fever of 102 degrees F or higher, frequent vomiting, six or more episodes of loose stools in 24 hours, severe abdominal or rectal pain, stools that are black and tarry, or blood or pus in the stools.

A Word From Verywell

Diarrhea may be an inconvenience that is soon gone, or it can be a serious or long-lasting illness. When you have a bout, be sure you are drinking enough fluids and see your doctor if it persists.